Delay line



S. YANDO DELAY LINE June 14, 1960 Filed Aug. 15, 1958 854M DFFL ECTION CONTROL SIGN/11.

BEAM INTENSITY CONTROL .F/GNAL INVENTOR STFPHEIV V i/V00 BY W ATTQRNEY DELAY LINE Stephen Yando, Huntington, N.Y., assignor, by niesne assignments, to Sylvania Electric Products Inc.-, Wilmington, Del., a corporation of Delaware Filed Aug. 15, 1958, Ser. No. 755,331

8 Claims. (Cl. 315- 3) My invention relates to signal delay lines.

Signal delay lines find a wide range of application in numerous electronic arts. The purpose of a delay line is to reduce the velocity of signal propagation therein and thus delay signal transmission for a predetermined period of time.

One type of signal delay line, known as an ultrasonic delay line, is frequently used to delay electrical signals in this manner. In this type of device, a first electrical signal is first transformed by a first transducer to a mechanical vibration; this vibration then propagates in the form to the beam intensity appears between the two electrodes of this pair.

of an acoustical wave through suitable transmission media to a second transducer; and the second transducer transforms the wave into a second electrical signal.

In my copending patent application Serial No. 738,469, filed May 28, 1958, now abandoned, I disclosed a ne type of delay line wherein the transmission media not only supports wave propagation but also serves an additional function; i.e. it respectively transforms electrical signals and acoustic waves into the corresponding acoustic wave and electrical signal equivalents. Hence, this acoustic delay line eliminates the necessity of using separate transducers.

However, this delay line introduces a fixed time delay; i.e. for a given delay line the path length of the acoustic wave is fixed and constant, and the propagation velocity of the wave is also fixed and constant. In contradistinction, I have invented an acoustic delay line in which the path length of the ultrasonic wave is varied in accordance With the variations of a variable control signal, and hence, the signal delay period of the line also varies in accordance with the control signal.

In accordance with the principles of the present in .vention, I provide an elongated strip of piezoelectric material. I further provide a 2N plurality of electrodes where N is any integer, the even numbered electrodes being secured to one surface of the strip at spaced apart locations. Similarly, the odd numbered electrodes are secured to the opposite surface of the strips at corresponding spaced apart locations whereby each odd numbered electrode is positioned opposite a corresponding even numbered electrode. The electrode pair adjacent a selected end of the strip constitutes an output electrode pair; each of the remaining electrode pairs constitute an input electrode pair. The ends of the strip are terminated .in such manner as to absorb, substantially without reflection, any incident acoustical energy.

I further provide (N-1) resistors, each resistor being electrically connected between the electrodes of the cor- -responding input electrode pair. trodes of each input electrode pairs are coupled in corn- Corresponding elecmon to a terminal maintained at a first potential.

An electron beam generated at a second and lower po- 3 itential is directed upon one surface of the strip. When the beam impinges upon an electrode of any input electrode pair, a current flowsin the resistor corresponding.

to this pair. Consequently, a first voltage proportional Due to the piezoelectric characteristic of the strip, an electric field is established within the region of 'the strip between these two electrodes. This field produces a mechanical strain proportional to the field intensity... As this strain changes, a mechanical stress proportional to the change in strain with time, i.e. a vibration proportional to the time rate of change of strain and hence proportional to the first time derivative of the first voltage, propagates along the strip in the form of first and second oppositely directed acoustic waves travelling toward corresponding ends of the strip and being absorbed there'at. One of these waves passes through a region of the strip between the twooutputelectrodes prior to absorption.

Due to the piezoelectric characteristics of the strip, an output voltage appears between the two output electrode: 'as this wave passes through a region of the strip between the output electrodes. The output signal is proportional to the mechanical stress, and hence is proportional to the first time derivative of the first voltage. Further, the output signal is delayed in time with respect to the first voltage, the delay period being determined by the time required for the acoustic wave to travel between the appropriate input electrode pair and the output electrode pair. Since, for any given material and geometry of the piezoelectric strip the velocity of wave propagation is constant, this delay period is determined by the physical separation between the above identified electrode pairs. By means of a suitable deflection circuit, the beam is directed upon one or another of the input electrodes in accordance with the variations in a control signal applied to the circuit, and thus the delay period is varied accordingly.

An illustrative embodiment of my invention will now be described with reference to the accompanying drawings wherein: Y

Fig. 1 illustrates a delay line in accordance with my invention; and

Fig. 2 shows a tube incorporating the delay line of Fig. 1.

, Referring now to Figs. 1 and 2, there is shown an evacuated cathode ray tube envelope 34. An electron gun 3 6', maintained at ground potential, produces an electron beam. The intensity of the beam is controlled applying a suitable intensity control signal to the terminals 46 of a control electrode 38 in the path of the beam. The beam thereafter passes between deflection electrodes 40 and thereafter impinges upon a target 10.

Target 10 includes a thin strip 14 or ribbon of piezoelectric material; in this example, the material is barium titanate. A 2N plurality of electrodes, in this example, electrodes 16, 18, 20, 22, 24, 26, 28 and 30, extend transversely of the long axis of the strip. The alternate numbered electrodes 16, 20, 24 and 28, are secured to one surface of the strip at positions intermediateits ends. The alternate electrodes 18, 22, 26 andst) are secured to the opposite surface of the strip at positions opposite the corresponding odd numbered electrodes. Electrodes 28-30 constitute an output electrode pair. Electrode pairs Iii-18, 20-22, and 24-26 respectively constitute input electrode pairs.

Separate resistors 32 are connected between the electrodes of each of the corresponding input electrode pairs.

' Further a selected electrode of each input electrode'pair,

Patented June 14-, 1960 1 shown by terminations 12. More particularly, the piezoelectric material has a characteristic acoustical impedance Z and the terminations must be formed from another material having a similarcharacteristie impedance. If this other material had exactly the same characteristic impedance as the strip, the terminations would have the "same cross sectional shape as the strip and would. be attached to theends of a strip essentially as a continuation of the strip. When the other material has a characteristic impedance which is not equal to that of the strip, a non-reflective termination canbe made by coating the ends and immediately adjacent portions of the strip with this material, as is shown in Figl. In thisexample, the material is lead which has a characteristic acoustical impedance which does not equal the characteristicimpedance of barium titanate. 7

When the beam is directed upon a selected input electrode as for example electrode :18, a current flows through resistor 32, and a first voltage proportional to the beam intensity appears between electrodes 16 and 18. This voltage establishes a first electric field'in astrip region intermediate electrodes 16 and 18. The electric field vector points along a line perpendicular to both electrodes, the field direction being determined by the instantaneous polarity of thefirst voltage. More particularly, the first electric vector always points from the electrode of lower positive potential toward the electrode of higher positive potential. The absolutevalue of the first electric field vector, which designates the field intensity, is proportional to the instantaneous value of the first voltage.

Due tothe piezoelectric characteristics of strip 14, the

" electric field produces in the strip region previously men-.

' tioned a mechanical strain proportional to the instantaneous field intensity and hence proportion-alto the instantaneous value of the first voltage. This strain produces a mechanical stress proportional to the time rate of change of the strain andhence proportional to the.

" first time derivative of the-firstvoltage. This stress propagates along the strip in the form of first and second oppositely directed acoustic wavestravellingtoward the left hand and right hand ends respectively of strip 14.

These waves are absorbed, substantially without reflec- 'tion, in terminations 12; i.e. due to the piezoelectric characteristics of strip 14, as the second ;wave passes through a second strip region intermediate the output j electrodesj28 and 30 at a time T later than T a second 7 electric field is established within this second region.

The first electric field vector, at time T points ina.

given direction. The second electric field vector, at time T points in the same direction. Moreover, the absolute value of the second electric field vector at time T is proportional to the first time derivative of the first electric field vector at time T1. output voltage appears between electrodes 28 and30. The instantaneous polarity of the'output voltage at time T is the same as the instantaneous polarity of the first I voltage at time T Moreoventhe instantaneousv value Consequently, a second or the characteristics of the material and the type of acoustic wave employed, More particularly, the acoustic wave can be either longitudinal (i.e. compression wave) or transverse (Le. a shear wave). When polycrystalline barium titanate is polarized in a direction parallel to the long axis of the strip, the acoustic wave produced therein will be longitudinal and will propagate at a velocity of approximately 5000 meters per second. -When the titanate is polarized in a direction perpendicular to the trodes of the corresponding input electrode pair, correlong axis of the strip, the acoustic wave can possess both transverse and longitudinal components. The velocity of the longitudinal component remains at about 5000 meters per second, but the velocity of the transverse component will be about 2500 meters per second.

In addition to polycrystalline barium titanate which is rendered piezoelectric by electric field polarization, any other piezoelectric material either polycrystalline or single crystal can be used; For example, other single crystal materials arequartz, Rochelle salts and ammonium dihydrogen phosphate, and the polycrystalline materials are lead zirconate-lead titanate mixtures.

What is claimed is:

l. A signal delay line comprising an elongated strip of piezoelectric material; a 2N plurality of electrodes where N is any integer, the even numbered electrodes being secured to one surface of said strip at spaced apart locations, the odd numbered electrodes being secured to the other surface of said strip at corresponding spaced apart locations, whereby each odd numbered electrode is positioned opposite a corresponding even numbered electrode,

' there being N different pairs of opposed electrodes; one

selected electrode, pair adjacent one end of said strip being an output electrode pair, the remaining (N-l) electrode pairs being input electrode pairs; a (N -l) plurality of resistors, each resistor being coupled between the elecsponding electrodes of said input electrode pairs being Tcoupled to a common terminal; first and second terminations aifixed to corresponding ends of said strip, said terminations absorbing substantially without reflection any incidentaccoustical energy supplied thereto from said 1 strip, and means to selectively direct an electron beam upon one of said strip surfaces.

7 2. A signaldelayline comprising an elongated strip of piezoelectric material; 2N plurality of electrodes where N is any integer, the evennumbered electrodes being secured to one surface of said strip at spaced apart locations, the oddnum-bered electrodes being. secured to the other surface'of said strip at corresponding spaced apart locations, whereby each odd numbered electrode ,is positioned opposite a corresponding even numbered j electrode, there being N different pairs of opposed electrodes; one selected electrode pair adjacent one end of said strip being an output electrode pair, the remaining (N1) electrode pairs being input electrode pairs; a (N '1) plurality of resistors, each resistor being coupled 'between the electrodes of'the corresponding input elecof the output voltage at time T is proportional to the I at time T the signal delay period being equal to the difference T -T L p A deflection control voltage is applied between ter- "minals 48 coupled to deflection electrodes 40 and controls the beam position accordingly. More particularly,

as the value of the control voltage changes, the beam can be appropriately directed upon any selected onehof electrodes 18, 22. and 26, and the. delay period (since the velocity of wave propagation is constant) will be varied L. in accordance with the physical separation of the selected electrode and the output electrode pair. 7 1 i The velocity of propagation determined both by trode pair, corresponding electrodes of said input electrode pairs being coupled to a common terminal; first and second terminations affixed to corresponding ends of said strip, said terminations absorbing substantially Without reflection any incident acoustical energy supplied thereto from said" strip; means to direct an electron 'beam upon one of said strip surfaces, and deflection means responsive to a control signal to accordingly deflect said beam along the long axis of said strip.

r 3. A signal delay line comprising an elongated strip -.of piezoelectric material; a ZN'plurality of-electrodes where N is any integen-the even numbered electrodes being secured to one surface of said strip at spaced apart locations, the odd numbered electrodes being secured to the other surface of said strip at corresponding spaced apart locations, whereby each .odd numberedelect'rode 7 .is positioned opposite a corresponding even numbered electrode therebeing N different pairs of opposed electrodes, one selected electrode pair adjacent one end of said strip being an output electrode pair, the remaining (N l) electrode pairs being input electrode pairs; a (N1) plurality of resistors, each resistor being coupled between the electrodes of the corresponding input electrode pair, corresponding electrodes of said input electrode pairs being coupled to a common terminal, said common terminal being maintained at a first potential; and an electron gun for producing an electron beam, said beam impinging upon a selected one of said strip surfaces, said gun being maintained at a second and lower potential.

4. A signal delay line comprising an elongated strip of piezoelectric material; a 2N plurality of electrodes where N is any integer, the even numbered electrodes being secured to one surface of said strip at spaced apart locations, the odd numbered electrodes being secured to the other surface of said strip at corresponding spaced apart locations, whereby each odd numbered electrode is positioned opposite a corresponding even numbered electrode, there being N different pairs of opposed electrodes, one selected electrode pair adjacent one end of said strip being an output electrode pair, the remaining (N--l) electrode pairs being input electrode pairs; a (Nl) plurality of resistors, each resistor being coupled between the electrodes of the corresponding input electrode pair, corresponding electrodes of said input electrode pairs being coupled to a common terminal, said common terminal being maintained at a first potential; an electron gun for producing an electron beam, said beam impinging upon a. selected one of said strip surfaces, said gun being maintained at a second and lower potential, and means responsive to a control signal to vary the intensity of said beam.

5. A signal delay line comprising an elongated strip of piezoelectric material; a 2N plurality of electrodes where N is any integer, the even numbered electrodes being secured to one surface of said strip at spaced apart locations, the odd numbered electrodes being secured to the other surface of said strip at corresponding spaced apart locations, whereby each odd numbered electrode is positioned opposite a corresponding even numbered electrode, there being N difierent pairs of opposed electrodes, one selected electrode pair adjacent one end of said strip being an output electrode pair, the remaining (N 1) electrode pairs being input electrode pairs; a (N- l) plurality of resistors, each resistor being coupled between the electrodes of the corresponding input electrode pair, corresponding electrodes of said input electrode pairs being coupled to a common terminal, said common terminal being maintained at a first potential; an electron gun for producing an electron beam, said beam impinging upon a selected one of said strip surfaces, said gun being maintained at a second and lower potential, and beam deflection means responsive to a control signal to deflect said beam back and forth along the long axis of said strip in accordance with said signal.

6. In combination, an electron gun for producing an electron beam, said gun being maintained at a first potential; a target in the path of said beam, said target being constituted by a signal delay line comprising an elongated strip of piezoelectric material; a 2N plurality of electrodes where -N is any integer, the even numbered electrodes being secured to one surface of said strip at spaced apart locations, the odd numbered electrodes being secured to the other surface of said strip at corresponding spaced apart locations, whereby each odd numbered electrode is positioned opposite a corresponding even numbered electrode, there being N difierent pairs of opposed electrodes; one selected electrode pair adjacent one end of said strip being an output electrode pair, the remaining (N-l) electrode pairs being input electrode pairs; at (Nl) plurality of resistors, each resistor being coupled between the electrodes of the corresponding input electrode pair, corresponding electrodes of said input electrode pairs being coupled to a common terminal; first and second terminations affixed to corresponding ends of said strip, said terminations absorbing substantially without reflection any incident acoustical energy supplied thereto from said strip; said common terminal being maintained at a second and higher potential, said beam impinging upon a selected surface of said strip, said beam when impinging upon an electrode of any input electrode pair producing a first voltage across said pair, said first voltage being proportional to the intensity of said beam whereby an acoustic wave propagates through said strip at a fixed velocity from a region inter mediate the electrodes of said any input pair to a region intermediate the electrodes of said output pair, and a second voltage proportional to the first time derivative of said first voltage but delayed in time with respect thereto appears between the electrodes of said output pair, the delay period being proportional to the separation between said any input pair and said output pair.

7. A signal delay device comprising an evacuated envelope; an electron gun located at one end of said envelope for producing an electron beam; a target in the path of said electron beam, said target including an elongated strip of piezoelectric material, a 2N plurality of electrodes where N is any integer, the even numbered electrodes being secured to one surface of said strip at spaced apart locations, the odd numbered electrodes being secured to the other surface of said strip at corresponding spaced apart locations, at least one electrode pair being an output electrode pair, the remaining electrode pairs being input electrode pairs; a plurality of resistors, one of said resistors being connected between the electrodes of each input electrode pair; a common terminal connected to each of said plurality of resistors, said common terminal being maintained at a more positive potential than said electron gun, and beam deflection means located intermediate said electron gun and said target, said beam deflection means causing said electron beam to impinge upon selected tanget electrodes in response to an applied control signal.

8. The signal delay device defined in claim 7 wherein beam intensitiy control means are coupled to said electron gun for varying the intensity of said electron beam.

References Cited in the file of this patent UNITED STATES PATENTS 2,307,438 Whitaker Jan. 5, 1943 2,361,998 Fleming-Williams Nov. 7, 1944 2,557,979 Labin June 26, 1951 2,640,925 Hirsch June 2, 1953 2,654,071 Harris Sept. 29, 1953 2,793,288 Pulvari May 21, 1957 2,806,155 Rotkin Sept. 10, 1957 2,828,470 Mason Mar. 25, 1958 FOREIGN PATENTS 156,243 Australia Apr. 28, 1954 

